BSS Audio MSR-604ii User Manual version v1.4
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1Introduction
It is not uncommon within a sound system which uses microphones as a source of
program, for that microphone to be connected to the input of a number of different
processing facilities.
An example of this would be in sound reinforcement work where a stage
microphone is required to drive the main ‘front of house’ mixing console, the stage
monitoring mixing console, a mobile recording studio and quite possibly an
outside broadcast recording vehicle. It is also common within such a system for the
microphone to be connected to considerable lengths of shielded cable before
being terminated at the processing facilities input connector. Such a load on the
microphone is very much in excess of its design capability, and as a consequence
the level and quality of the sound is impaired.
A further complication can arise within such a system from multiple earthing as
each of the processing facilities would be providing its own ground. To overcome
these problems it is quite common for a multiple winding transformer to be used
which provides separate secondary windings for each of the required outputs. This
solution will solve the multiple grounding problems, however it does not tackle the
sound level and quality problem as, being a passive device, it has no power
amplification capability.
Cost effective active electronic solutions proved elusive until the introduction of
the original BSS MSR-604 overcame the problems of noise and headroom. The
current MSR-604ii further improves upon the performance of the original unit with
yet greater dynamic range, flexibility of gain and level control, internal bus routing,
signal metering and a headphone monitoring facility.
The MSR-604ii is a four channel, four way signal splitting package and the MSR-
602ii is the system power supply capable of supplying power for 40 channels, that
is, 10 separate MSR-604ii units.
1.1 MSR-604ii Mic/line signal splitter
The MSR-604ii has four channels, each of which may be isolated and used totally
independently from the next or, by internal re-configuration, be interconnected to
form distribution amplifier sections with a single input driving up to 64 outputs.
The low noise floor requirement necessitates a remote power supply system, the
MSR-602ii, which provides the required DC voltages.
A MIC/LINE switch introduces a 20dB input pad, which in combination with the 5
step GAIN switch allows any input signal below + 33dBu to be perfectly matched
to the MSR-604iis dynamic range. The setting up process is further assisted by the
provision of a momentary LISTEN switch which routes the signal to a calibrated
HEADROOM meter and a headphone monitor amplifier built into the MSR-602ii
power supply unit. Each channel also has a CLIP LED to give constant warning
against signal overdrive. As a further refinement a separate 10dB input pad may be
